K2 is the newest in a long line of synthetic drugs being abused these days.  It's chemical structure is similar to marijuana.  The effects are hallucinations, anxiety.  The problem with K2 is that it can be deadly--several individuals have found themselves in emergency rooms with brain swelling, seizures and aneurysms.   K2 cannot be detected by regular urine drug screens, and until recently has been a legal substance available for purchase as "incense" in many stores.  As more young people die, states are making the substance illegal.